Heat-controlling apparatus for electrical furnaces



Jan. 6. 1925. 1,522,122

1 A. HEIDBRINK ET AL HEAT CONTROLLING APPARATUS FOR ELECTRICAL FURNACES Filed April 21, 1921 4 Sheets-Sheet 1 .Z'N YEN TORS. J'AY A. HE/DBRINK. CHARLES W fZETCHER.

86 WMMMM A TTOFPNE Y6.

Jan. 6. 1925. 1,522,122

J. A. HE1DBRINK ET AL HEAT CONTROLLING APPARATUS FOR ELECTRICAL FURNACES 4 Sheets-Sheet 2 Filed April 21, 1921 IN vs/v TORS.

JAY A. HE/DBRINK.

CHARLES W fZETCHE/P:

BY M4 in ATTORNEY-5.

Jan. 6. 1925. 1,522,122

v J. A. HEIDBRINK ET AL HEAT CONTROLLING APPARATUS FOR ELECTRICAL FURNACES Filed April 21, 1921 4 Sheets-sheet a F m mo hi2? w 94 gtpftf.

JA A. HE/OBFF/N/f. CHARLES W FLETCHER:

BYWMM A T TOR/v: Y8.

I N VEN ToRs;

Jan. 1925- 1',522,122

J. A. HEIDBRINK ET AL HEAT CONTROLLING APPARATUS FOR ELECTRICAL FURNACES Filed April 21, 1921 4 SheetsSheet 4 JA A. HEIDBRr/vrr. CHARLES W FLETCHER.

ATTORNEYS.

Patented Jan. 6, 1925.

JAY A. HEIDBRINK AND CHARLES V1. FLETCZ-I B, 015 MINNEAPOLIS, MINNESOTA;

SAID FLETCHER- ASSEGNOR T9 SAID HEIDBRINK.

HEAT-CONTRGLLING APPARATUEQ FGl-t ELECTRICAL FURNACES.

Application filed April 21, 1921.

To all whom it may concern:

Be it known that we, JAY A. l-lnmniiiivn and Cunnrns JV. FLETCHER, citizens of the United States, residing at h linneapolis, in the county of Hennepin and State of Minnesota, have invented certain new and useful Improvements in Heat-Controlling Apparatus for Electrical Furnaces. of which the following is a specification.

()ur invention relates to heat controlling apparatus for electrical furnaces. The type of furnace which we have in mind particularly is that employed by dentists for burning out invested models in moulds which are to be used for making dental castings. An object of our invention is to provide for maintaining a constant temperature in a furnace heated by an electrical resistance device by synchronously controlling the passage of current through said resist ance device and through a resistance coil associated with a thermostat which, by its expansion automatically cuts off the current from both resistances when the temperature in the furnace reaches a desired maximum and which, by its contraction, re-establishes the passage of current through the resistances. Another object is to provide means by which the temperature to be maintained in the furnace may be varied at will so that the desired maximum may be greater or smaller as desired. An object in general is to provide thermostatic means for controlling the amount of electrical energy deli ered to an electrical element or device over an extended period of time regardless of variations in the voltage of the source of energy. The full objects and advantages of our invention will appear in connection with the detailed description, and the novel features embodied in our inventive idea will be particularly pointed out in the claims. In the accompanying drawings which illus trate a practical embodiment of our invention,Fig. 1 is an elevational view of our apparatus connected to an electrical dental furnace, the latter being shown in vertical section. Fig. 2 is a vertical sectional view of our apparatus. Fig. 8 is a view of a sli ht modification, the upper portion of this View being in section corresponding to that shown in Fig. 2 and the lower portion having the outside casing plate in place. Fig. 4 is a view in vertical section on the line ll of Fig. 2. Fig. 5 is a View in hori- Serial No. 463,260;

section'on the line 55 of-Fi 2. is a view in horizontal section on the line 6-6 of Fig. 2. Fig. 7 is a view in hori zontal section on the line 'i'7 of Fig. 2. Fig. 8 is an end view of a commutator. 9 embodies a wiring diagram showing the passage of current at the beginning when the thermostat is cold and in contracted position. Fig. 10 embodies a wiring diagram showing the passage of electric current through divided circuits when the device has been placed in its operative position by means of a current passing through a solenoid. Fig. 11 embodies a wiring diagram showing the passage of current through the solenoid when the thermostat has been fully expanded.

Referring to the construction shown in the drawings, the letter F in Fig. 1 designates in general an electrical furnace such as that disclosed in the patent to T. W. Maves, Reissued Number 14,730, in the lower portion of which is a resistance device or coil 12, the ends of which are connccted by wires 14 and 16 with metallic bars 18 and 20 respectively. As shown in F ig. 1, the furnace is lined with heat insulating material. A main wire 22 is connected to the bar 18 and the other main wire 2% is connected to a bar 26. These three bars and also fourth bar 28 are secured in spaced relation to a piece of iiisulating material 30 which is secured to the inside of one of the walls of a casing 32 as best shown in Figs. 2 and l. This casing is divided by a horizontal partition 34: into lower and upper compartments 86 and 38. The walls of the upper compartment 38 are lined with heat insulating material a0 and mounted in this compartment is a thermostat, the fixed members 42 and 44: of which are adjustably mounted in posts so and %8 which are insulated from the casing. The movable member of the thermostat is insulatively mounted so as to lie between the members 42 and 4A and is connected by a wire 52 with the bar 28. Rotatably mounted in the lower compart ment 36 is a commutator which includes a cylinder 54 of insulating material in the periphery of which are embedded three equally spaced contact plates 56. Secured to rotate with the cylinder 54 is a ratchet disk 58 having six teeth around its periphery. Oscillatingly mounted at one of zontal rue A its ends on a trunnion of the cylinder 5-1 is an arm 60 which carries a pawl 62 adapted to engage the teeth of the ratchet disk. The other end of the arm 60 is pivotally connected with the lower end of a solenoid core 6-1 which is adapted to cooperate with a solenoid 66 having a coil 68, the ends of which are connected by wires 70 and 72 with the bars 28 and 18 respectively. Insulatively mounted above the commutator cylinder 54 in spaced relation to each other and adapted to be bridged by the contact plates 56 as they are rotated are a pair of contact fingers 74 and 76, the finger 7a being connected by a wire 7 8 with the bar 26 and the finger 7 6 being connected by a Wire 80 with the post 18 of the thermostat. Insulatively mounted below the cylinder 51 in spaced relation to each other and adapted to be bridged by the contact plates 56 during their rotation are a second pair of contact fingers 82 and 84, the finger 82 being connected by a wire 86 with the bar 20 and the linger 8 1 being connected by a Wire 88 with the finger H. The four fingers are secured to a plate of insulating material 89. The post 16 of the thermostat is connected by a wire 90 with the bar 20, and the bar 18 is connected by a Wire 92 with one end of a resistance coil 94, the other end of which is connected by a wire 96 to the wire 90 at a point near the attachment of the latter to the post 16 or it may be attached directly to this post. The movable member 50 of the thermostat is attached to a cylindrical block 98 of insulating material. Secured to this block is an arm 100, the free end of which is attached to a rod 102 having a threaded portion engaging the internally threaded surface of a sleeve 104. which carries a knob 106 on its outer end. The sleeve 10% extends through a bearing member 108 held in an opening in the casing by a nut 11.0 and the sleeve 1041 is rotatably held by anut 112 threaded upon its inner end and engaging the inner end of the bearing member 108. In the slight modification shown in Fig. 8, the posts +16 and 18 are insulatively mounted on a triangular plate 11s pivoted at 116. A rod 118 is attached to this plate and the outer end of this rod is attached and connected up for operation in the same manner as the rod 102. It is obvious that upon turning the knob 106 in either of these forms the relation of the movable member and the fixed members of the thermostat will be changed so that the thermostat may be made to operate at ditferent temperatures whereby the constant temperature to be maintained in the furnace. may be varied as desired.

The operation and adiantages of our invention will be readily under ood from the foregoing description. The articles to be heated are placed in the furnace F and the current from the main line is turned on. Assuming that the thermostat is cold and the lingers 7 1: and T6 are bridged by one of the contact plates 50 as shown in Fig. 9 current 1 pass from the main line 22 through the 18 wire 2 solenoid coil 08, wire 70. to 28, wire 32, movable contact member wire 80, finger 76, contact plate 56. finger wire 78 bar 20, and main line 2st. The crrent passing through the solenoid coil 00 causes its core 64: to be. drawn up and more the cylinder 5% through one-sixth of a rotation which removes the contact plate from engagement with the fingers 74 and 7 0 and causes a contact plate 30 to bridge the fingers and 84. as sl'iown in Fig. 10. The ci cnit through the solenoid coil (38 is broken thereby and the core (34: will drop by gravity. The current from the main line then passes to the bar 18 where it divides. ()ne portion of the current goes through the wire it, resistance coil 12, and wire 10 to the bar 20. Another portion goes from the bar 18 through the wire 92, resistance coil 94, wire 90 and wire 90 to the bar 20 where it j ins the current through the other circuit, and the combined current passes through the wire 86, finger 82, contact plate fin- 81. wire 88, wire 78, bar 20 and main line 2-1. The current passing through the lt nice coii 12 heats the furnace and the out passing through the resistance coil 0? beats the thermostat and causes it to expand. When the desired maximum temperature in the furnai'tc is reachml. depending upon the setting of the thermostat. the mov a ble thermostat member .30 engages the fixed *ernber 42 as shown in Fig. 11. Current then passes from the main line through the bar 18, wire T2, solenoid coil 08. wire 70. p 28, wire 12. movable thermostat mem her 530. wire 90. bar 20. wire 80, linger 82, contact ilate 536 finger 81 wire 88. wire 78 l t. a

r and main line 21. The current is shunted so as not to pass through istanee coils 12 and 9-1. and at the n time the current through the solenoid 08 draws up the coil (3%, causing the cylinder alto rotate another one-sixth of a rewolution andrenioa s the contact plate 56 from ment iii the fingers 82 and plate 50 into engagethe lii'igers 70. This operation current througi the apparatus the core ll drops by gravitv The curemains oil until the mo\ able thermw 'iember 50 contracts suliiciently to onhe fixed member when the elements again be in the position shown in Fig.

\vf'l f and the cycle of UPGI'fltlUHS previously The movable .at member 60. therefore, oscillates the fixed members 1-2 and -14. and e the thermostat is sensitive to small de cribed will be repeated. l'llil'l lOf variations in temperature, the temperature in the furnace will be maintained subst tially constant. It will be understood when our controlling apparatus is used in connection with a furnace, the 'l urnace r her as well as the cha-n'iber containin thermostat should be surrounded w th insulating material. However, the of electrical energy delivered to the e device receiving electricity ll me whether or not said tier-rim protecte with heat insnlatinc iv e claim:

1. A heat controlling apparatus for t naces heated by an electrical resistance de vice comprising a thermostat, acircuit for said electrical. resistance device, an electra magnetic device, an armature adapted to be partially rotated each time said electromagnetic device is energized, means for causing current to flow through said resist ance device when said armature is positioned in one manner and for causing cur rent to be cut when said armature is given a partial. rotation into another position, and connections associated with said thermostat and said electromagnetic device whereby the latter will be energized both when the movable member of said thermostat is expanded into contact with one of the fixed members thereof and when it comes into contact with the other oi the lined members thereof.

2. A heat controlling apparatus for furnaces heated by an electrical resistance de vice comprising a thermostat, a resistance coil adjacent said thermostat, an electromagnetic device, circuits through said re sistance device and said resistance coil, an armature adapted to be partially rotated each time said electro-magnetic device is energized, means "for causing current to flow through said resistance device and said coil when said armature is po- IGSlSi 2111(26 sitioned in one manner and for causing the current to be cut oii when said armaure is gii'en a partial rotation into another posit-ion, and connections associated with said thermostat and said elec'tro-magnctic device whereby the latter will be energized both when the movable member oi said thermostat is expanded into contact with no: of the first mention d pair of contact in a wire conn' the other of said contact lingers with the fourth bar, a conn ting said last mentioned contact linger with one of the second mentioned pair or contact fingers, and a wire connecting the other oi? said second mentioned pair out contact lingers and a wire connecting the other oi said second mentioned pair or contact fingers with the third 1 car.

apparatus for foran electrical resistance dethermostat, a resistance thermostat, solenoid, a a plurality of equally insulatively mounted pair of contact itcd at r side of said armature ed to dged by said contact aloud of contact lingers loside of said armature bridged in alternation Y of adapt '1 "ontact lingers by ans connected with said solenoid for imparting to "rid armature a step-by-step rotation, the ex- 1 t 'hich is one-halt the spacing besaid contact plates, tour insulatively mounted spaced bars, the second and fourth liars being connected with the main electrical line, a circuit through the coil 0i? said solenoid connected with the first and second bars, a circuit through the resistance device ot the furnace connected with the second and third bars wire connecting one of the fixed members of said thermostat and the third er, a circuit through said resistance coil of the thermostat connecting the second bar and said last mentioned wire, a wire connecting "the movable member of said thern'iostat and the first bar, a wire connecting the other ilxed member of said therhe t controlling apparatus for furh an electrical resistance dethermostat, a resistance thermostat, solenoid, a

a plurality of equally ulatively mounted said armature, a pair ed at one side of said to be bridged by said pair of contact l' BSitQ side oil said ited to he bridged in alt ,d first pair of contact h, y said contact plates, a ratchet vn teeth in number twice the aid contact plates, an arzn end, a pawl on said arm age said ratchet wheel and ature h an angular t. i'orresponding to one of said teeth upon each "forward movement of said arm, 1 latter hc n connected at its other end 1 core o't said solenoid, tour A mounted spaced bars, the second rth hars being connected with the :al line, circuit through the i ioienoid connected with the first 1 bars, circuit throu h the re I l b ,t device ot the turnace connected with the second and third bars, a wire connecting on of the fixed members of said thermostat and the third bar, a circuit dufoim'li said resis ance COll oi: the thermo- .1 t connecting the second bar and said last mentioned wire, a wire connecting the movaol member said thermostat and the first bar, a wire. connecting the other fixed memher of said thermostat and one of the first mentioned pair oi? contact fingers, a wire connecting the other of said pair of contact fingers with the fourth bar, a wire connecting said last mentioned contact finger with one of the second mentioned. pair of contact and a 1 thermostat, a solenoid, a 'tihir'iililt! armature or" insulating material j three equally spaced contact plates peri ohery a pair of contact fingers at one side of said armature adapte hridejed by said contact plates, at l oi "or t: ct plates located at the Main armature and adapted 1 alternation with said first lingers by said contact i ratchet wheel fixed to said niroted at one end on a armature, a pawl on said engage said ratchet teeth turn said inimature through one-sixth :1 rotation upon each forward movement arm, the latter being connected at end to the movable core of said i, tour latively mounted spaced the second and fourth bars being conwith the main electrical line, a cirthrough the coil oi said solenoid cond with the iirst and second bars, a cirthrough the resistance device of the "'i'irnace conue: ted with the second and third a wire connecting; one of the fixed mcnihors ot said thermostat and the third bar. a circuit through said resistance coil of the thermostat connecting the second bar and said last mentioned wire, a wire connecting the movable member of said thermostat and the first bar, a wire connecting the other fixed member of said. thermostat and one of the first mentioned pair of cont ct fingers a wire connecting the other of said pair of contact fingers with the fourth bar, a wire connecting said last mentioned contact finger with one of the second mentioned pair of contact fingers, and a wire connecting the other of said second mentioned pair of contact fingers with the third bar.

In testimoirx whereof" we hereunto affix our signatures JAY A. HEIDBRIN K. (/HARLES V. FLETCHER. 

